Method of producing a container closure

ABSTRACT

A method of producing a liquid container closure includes the acts of providing a cap and molding a cap liner on an interior surface of the cap and a grip portion on an exterior surface of the cap.

BACKGROUND AND SUMMARY

The present disclosure relates to a closure for a liquid container, andparticularly to a closure configured to close an open mouth formed in athreaded neck of a beverage container. More particularly, the presentdisclosure relates to a method of producing a container closureincluding a sealing liner.

Milk, juice, and other beverages are dispensed into jugs or containersat a bottling plant. A closure is then mounted on the container neck toclose a liquid inlet/outlet opening formed in the container neck.Closures are sized and shaped to mate with container necks to minimizeleakage of liquid from a closed container during shipment of filledcontainers from a bottling plant to a wholesale or retail store.

Some beverage containers, such as one gallon milk or orange juice jugs,are extrusion blow-molded using a polyethylene plastics material. Otherbeverage containers of the type used to store “sport” drinks are stretchblow-molded using a PET plastics material. In most cases, externalthreads are formed on the open-mouth necks of these containers to matewith a container closure formed to include mating internal threads.

Container closures are usually made of low-density polyethylene (LDPE),high-density polyethylene (HDPE), or polypropylene (PP). Some closuresare configured to be snapped onto the neck using a capping machine atthe bottling plant and screwed on and off the neck by a consumer at homeor elsewhere. Such “snap-on, screw-off” style closures often includemany fine interior threads with many separate thread leads to enable abottler to close the open mouth formed in the container neck by applyingdownward pressure on the closure to “snap” it into place on the neck ofa filled container. Nevertheless, a consumer is able to twist andunscrew the threaded closure to remove it from the threaded neck of thecontainer to access the liquid in the container.

According to the present disclosure, a method of producing a liquidcontainer closure comprises the steps for providing a cap and molding amonolithic compliant member on the cap. The monolithic compliant memberincludes a cap liner located on an interior surface of the cap andadapted to mate with a neck of a liquid container received in aninterior region of the cap. The monolithic compliant member alsoincludes a grip portion on the exterior surface of the cap.

Additional features of the present disclosure will become apparent tothose skilled in the art upon consideration of the following detaileddescription of preferred embodiments exemplifying the best mode ofcarrying out the disclosure as presently perceived.

BRIEF DESCRIPTION OF THE DRAWINGS

The detailed description particularly refers to the accompanying figuresin which:

FIG. 1 is a perspective view of a closure in accordance with a firstembodiment of the present disclosure showing a cap mounted on a neck ofa container and showing a grip ring carried in an annular channel formedin a top perimeter portion of the cap to form the closure;

FIG. 2 is an exploded perspective assembly view of the closure andcontainer neck of FIG. 1 showing formation of a series of extrusionholes formed in a top surface of the cap and showing a monolithiccompliant member comprising a grip ring (to the right of the cap) and acap liner coupled to the grip ring by a series of circumferentiallyspaced-apart extrusion posts that are arranged to extend through theextrusion holes formed in the cap when the monolithic compliant memberis overmolded onto the cap as suggested in FIGS. 9-12 to produce theclosure shown in FIGS. 1 and 13-17;

FIG. 3 is a perspective view similar to FIG. 2 showing the closuremounted on the container neck and showing the monolithic compliantmember formed on the cap to provide an inner cap liner coupled to anouter grip ring by extrusion posts;

FIG. 4 is a perspective view of the cap of FIGS. 1-3;

FIG. 5 is a side elevation view of the cap of FIG. 4;

FIG. 6 is a top plan view of the cap of FIGS. 4 and 5;

FIG. 7 is a bottom view of the cap of FIGS. 4-6;

FIG. 8 is an enlarged sectional view taken along line 8-8 of FIG. 6;

FIG. 9 is a block diagram illustrating a process for using compressionmolding apparatus to form a monolithic compliant member comprising agrip ring and a cap liner on a cap to produce a closure;

FIG. 10 is a diagrammatic view showing a system for applying a plasticsmaterial to the cap preparatory to compression of that plastics materialto form a monolithic grip ring and cap liner on the cap;

FIG. 11 is a diagrammatic view showing components in a compressionmolding apparatus before movement of a punch to compress plasticsmaterial applied to the cap;

FIG. 12 is a diagrammatic view similar to FIG. 11 after movement of thepunch to compress plastics material applied to the cap to form amonolithic grip ring and cap liner component on the cap;

FIG. 13 is a perspective view of the closure of FIGS. 1-3;

FIG. 14 is a side elevation view of the closure of FIG. 13;

FIG. 15 is a top plan view of the closure of FIGS. 13 and 15;

FIG. 16 is a bottom view of the closure of FIGS. 13-15;

FIG. 17 is an enlarged sectional view taken along line 17-17 of FIG. 15showing the formation of the monolithic compliant member on the cap toform the inner cap liner and the outer grip ring;

FIG. 18 is a perspective view of a closure in accordance with anotherembodiment of the disclosure;

FIG. 19 is a sectional view taken along line 19-19 of FIG. 18;

FIG. 20 is a perspective view of a closure base included in the closureof FIG. 14 before a monolithic compliant member is overmolded onto thecap;

FIG. 21 is a sectional view taken along line 21-21 of FIG. 20;

FIG. 22 is a sectional view (similar to FIG. 19) of a closure inaccordance with another embodiment of the disclosure;

FIG. 23 is a partial perspective view of a cap included in the closureof FIG. 22 before a monolithic compliant member is overmolded onto thecap; and

FIG. 24 is a sectional view taken along line 24-24 of FIG. 23.

DETAILED DESCRIPTION

A monolithic compliant member 10 is coupled to a cap 12 to provide aliquid container closure 14 as suggested, for example, in FIGS. 1-3 andFIGS. 13-17. Closure 14 mounts on a neck 16 of a container 18 to closean open mouth 20 formed in neck 16. An illustrative compression-moldingprocess for forming monolithic compliant member 10 on cap 12 is shown inFIGS. 9-12.

Monolithic compliant member 10 includes a cap liner 11, a grip portion13 illustratively shaped to form a ring, and a series of posts 15coupled at one end to cap liner 11 and at another end to grip portion 13as suggested, for example, in FIGS. 2 and 3. Each post 15 is arranged toextend through a companion hole 17 formed in cap 12 to tether cap liner11 to grip portion 13 to retain monolithic compliant member 10 on cap 12in a manner shown, for example, in FIG. 3. It is within the scope ofthis disclosure to form grip portion 13 in suitable shapes other than aring.

Monolithic compliant member 10 is made of a compliant material thatyields elastically when a force is applied and thus is deformable toallow cap liner 11 to establish a sealed barrier located, for example,between cap 12 and neck 16 of container 18 upon installation of closure14 on neck 16 as suggested in FIGS. 1 and 3. Grip portion 13 is made ofthat same compliant material. One characteristic of the compliantmaterial is that it is adapted to move into and through voids formed incap 12 or associated with molds used to overmold monolithic compliantmember 10 onto cap 12. In one embodiment, the compliant material used toform grip portion 13 is “softer” than the material used to form cap 12.In an illustrative embodiment, grip portion 13 provides a high-friction,low-abrasion surface for contact with an end user during contact withclosure 14 to open and close container 18. It is within the scope ofthis disclosure to use a material having one color to form monolithiccompliant member 10 and a material having another color to form cap 12.

In the illustrated embodiment, cap liner 11 includes concentric firstand second seal rings 21, 22 that contact an upwardly facing surface 23of an annular rim 24 included in neck 16 to establish an “annular seal”therebetween when cap 12 is coupled to neck 16 (as shown in FIGS. 1, 3,and 12) so that leakage of liquid (not shown) from container 18 throughopen mouth 20 is blocked. Cap liner 11 also includes a mount 26 having atop surface 28 arranged to mate with cap 12 and an opposite bottomsurface 30 arranged to support the concentric first and second sealrings 21, 22 as suggested in FIGS. 4-6. In the illustrated embodiment,mount 26 is shaped to provide a round disk. It is within the scope ofthis disclosure to omit seal rings 21, 22 (and use a portion of mount 26to effect a seal) or employ one or more seal rings or members in capliner 11.

Mount 26 of cap liner 11 includes a round inner web 32 and an annularouter web 34 surrounding round inner web 32 as suggested in FIGS. 2 and19. Concentric first and second seal rings 21, 22 depend from annularouter web 34 as suggested in FIG. 19. Inner web 32 includes an outerperipheral portion terminating at first seal ring 21 to cause first sealring 21 to surround inner web 32. Inner web 32 includes a central dome36 formed to include a dome receiver cavity 38 having an opening in topsurface 28. Inner web 32 also includes a web membrane 40 arranged tosurround central dome 36 and extend radially outwardly from central dome36 to first seal ring 21.

Monolithic compliant member 10 is formed from a compliant material witha preferred Shore A durometer hardness of 58±3, although materials withhardness readings ranging from 24 to 95 are suitable. The preferredcompliant material is sold as ALPHA SEAL #01-372, available fromAlphaGary Corporation of Leominster, Mass. Examples of suitablematerials for use in monolithic compliant member 10 include synthetic ornatural rubber, ethylene vinyl alcohol (EVA), linear low-densitypolyethylene, thermoplastic elastomers, and/or soft polypropylene.Optionally, the material may be a laminate of one or more of suchcompounds or mixtures of one or more of such compounds.

Cap 12 includes a top wall 62, a grip support 63 extending around topwall 62, and an annular skirt 64 depending from grip support 63 to forman interior region 66 of cap 12 as shown, for example, in FIGS. 2 and10-12. Cap 12 also includes, for example, a tamper band 68 coupled toannular skirt 64 by means of frangible bridges 69 or other suitablefrangible connectors. It is within the scope of this disclosure to omittamper band 68 from cap 12.

Grip support 63 and top wall 62 cooperate to form a channel 65 receivinggrip portion 13 of monolithic compliant member 10 as shown, for example,in FIG. 4. Grip portion 13 is located outside of interior region 66 ofcap 12 and arranged to engage an exterior surface of cap 12 assuggested, for example, in FIG. 13. In the illustrated embodiment, thatexterior surface is defined by portions of grip support 63 and top wall62. As suggested in FIGS. 1-4, grip support 63 and a perimeter edge 61of top wall 62 cooperate to form an annular channel 65 and grip portion13 is ring-shaped and located in annular channel 65. It is within thescope of this disclosure to form grip portion 13 to establish an“endless” grip ring (as illustrated in FIGS. 1 and 2) or as one or moresegments located on an exterior surface of cap 12 and linked to capliner 11.

Referring now to FIGS. 4-6 and 8, in the illustrated embodiment, annularskirt 64 includes an upper edge 80. Grip support 63 includes an annularlateral wall 81 extending away from perimeter edge 61 of top wall 62 andmating with annular upper edge 80 of annular skirt 64. Annular upperedge 80 and an exterior surface of annular lateral wall 81 cooperate todefine a boundary of annular channel 65 formed in cap 12 and engage gripring 13 located in annular channel 65 as suggested in FIGS. 2 and 3.Annular skirt 64 is arranged as suggested in FIG. 8 to extend in avertical direction and annular lateral wall 81 is arranged to extend ina horizontal direction to lie in orthogonal relation to annular skirt64.

Annular lateral wall 81 of grip support 63 is formed to include“extrusion” holes 17 as suggested in FIGS. 2, 4, 6, 8, and 17. Asdisclosed herein, plastics material is moved or otherwise extrudedthrough holes 17 during formation of monolithic compliant member 10 oncap 12 to form closure 14.

In an illustrated embodiment suggested in FIGS. 4, 6, and 7, extrusionholes 17 are formed to lie in circumferentially spaced-apart relation toone another in a circular pattern around perimeter edge 61 of top wall62. It is within the scope of this disclosure to vary, for example, thesize, spacing, and number of these extrusion holes 17. Extrusion holes17 provide passageways through cap 12 for conducting plastics materialbetween annular channel 65 and interior region 66 during creation ofmonolithic compliant member 10 on cap 12. As suggested in FIGS. 2, 3,and 17, once monolithic compliant member 10 is established on cap 12,extrusion posts 15 extend through extrusion holes 17 to link cap liner11 to grip portion 13. Each of extrusion posts 15 provides means fortethering grip portion 13 to cap liner 11 to retain monolithic compliantmember 10 on cap 12. As suggested in FIG. 2, in one embodiment,extrusion posts 15 are arranged to extend vertically to lie inspaced-apart relation to one another.

In the illustrated embodiment, annular skirt 64 of cap 12 has a total offour threads 70 with four leads 71 formed in the inner surface 72 ofannular skirt 64. In this embodiment, the multiple threads and multiplethread leads assist in providing skirt 64 with sufficient flexibility toprovide a snap-on/twist-off capability. The multiple threads 70 arepreferably sized, angled, and pitched so that they can slide overcontainer neck threads 73 in response to downward axial pressure appliedduring bottling. A wide variety of numbers of threads having differinglength, height, pitch, and angle of opposite faces may be used in skirt64.

Preferably, cap 12 is made of high-density polyethylene (HDPE) resinhaving a density of about 0.95. It is further contemplated that caps 12may be formed from LDPE, a blend or copolymer of LDPE and HDPEpolypropylene (PP), or other lightweight, inexpensive thermoplasticmaterials suitable for use in compression-molding.

As can be best seen in FIGS. 5 and 8, frangible bridges 69 include bothangled bridges 69 a and vertical bridges 69 b connecting annular skirt64 to tamper band 68. Preferably, band 68 included at least eightbridges, including two pairs of angled bridges and two pairs of verticalbridges, although other combinations of bridges may be used. The loweredge of annular skirt 64 is defined by a shelf extending axiallyoutwardly so that it has a slightly greater exterior diameter than theremainder of annular skirt 64. A plurality of spaced-apart pads 59extend down from the lower edge of annular skirt 64. The outer diameterof pads 59 preferably match the outer diameter of the band 68. Pads 59provide a surface for the upper edge of band 68 to bear against whendownward axial pressure is applied to the cap during bottling and whenupward axial pressure is applied to the bottom edge of band 68 to assistin ejection of skirt 64 from an injection mold.

The exterior and interior diameters of tamper band 68 are slightlylarger than those of annular skirt 64 (other than at pads 59) to allowband 68 to fit over annular rim 24 on container neck 16. Band 68 has aplurality of ridges 75 formed on its interior surface 76. Ridges 75 havean angled lower surface 77 and a bridge-severing surface 78 extendingtransversely from interior surface 50. Lower surface 77 of ridges 75 areangled to ease passage of skirt 64 and band 68 over rim 24 on neck 16during the application of downward axial pressure on cap 12 in thecourse of bottling. Bridge-severing surface 78 of ridges 75 are designedto engage rim 24 on neck 16 of container 18 when cap 12 is twisted forremoval. The engagement between bridge-severing surface 78 and rim 24 onneck 16 as skirt 64 is lifted and rotated breaks frangible bridges 69 sothat band 68 is retained on neck 16 of container 18. Althoughbridge-severing surface 78 is shown as being disposed on a series ofspaced-apart ridges, it is contemplated that a continuousbridge-severing surface could be provided by use of a continuous rimextending transversely from the interior surface of band 68, rather thanspaced-apart ridges.

In the embodiment illustrated in FIGS. 18-21, a closure 114 includes acap 112 and a monolithic compliant member 110 formed to include externalgrip fingers 101 depending from a radially outwardly facing portion 102of grip portion 13. Cap 112 includes a top wall 62, an annular skirt164, and a tamper band 168. Annular skirt 94 is formed to includeupright channels 103 for receiving plastics material to define gripfingers 101 therein. Grip fingers 101 are illustratively arranged to liein circumferentially spaced-apart relation to one another in afrustoconical array as suggested in FIGS. 18 and 19.

In the embodiment illustrated in FIGS. 22-24, a closure 214 includes acap 212 and a monolithic compliant member 210. In this embodiment, cap212 includes a grip support 263 including an annular lateral wall 281and an annular upright wall 283. Annular lateral wall 281 extends fromperimeter edge 61 of top wall 62. Annular upright wall 283 extends fromthe outer edge of annular lateral wall 281 downwardly to mate with anannular upper edge 280 of annular skirt 264. In this embodiment,perimeter edge 61 of top wall 62, exterior surfaces of annular lateraland upright walls 281, 283, and annular upper edge 280 of annular skirt264 cooperate to define a boundary of annular channel 265 formed in cap212 and engage grip portion 213 located in annular channel 265.

In the embodiment of FIGS. 22-24, annular upright wall 283 is formed toinclude extrusion holes 17. Extrusion holes 17 are formed to extend inradially outwardly extending directions from a central vertical axis 201extending through top wall 62. Each extrusion post 15 extends throughone of extrusion holes 17 to tether cap liner 211 to grip portion 213 toretain monolithic compliant member 210 on cap 212. It is within thescope of this disclosure to form extrusion holes 17 in annular lateralwall 281. A sealing ring 221 is included in cap liner 211.

A method of producing a liquid container closure in accordance with thepresent disclosure comprises the steps for providing a cap 12 having aninterior surface defining an interior region 66, an exterior surfacelying outside interior region 66, and at least one hole or opening 17extending from the interior surface to the exterior surface and thenmoving a plastics material through the at least one hole 17 to create amonolithic compliant member 10 having (1) a cap liner 11 located on theinterior surface of cap 12 and adapted to mate with a neck 16 of aliquid container 18 received in interior region 66 of cap 12 and (2) agrip portion 13 on the exterior surface of cap 12. As suggested, forexample, in FIGS. 9-12, the moving step includes the steps of applying aplastics material 306 to the interior surface of cap 12 and thecompressing plastics material 306 to form cap liner 11 in interiorregion 66 of cap 12 and to form grip portion 13 on the exterior surfaceof cap 12. In illustrative embodiments, plastics material used to formmonolithic compliant member 10 is heated to a predetermined temperaturebefore it is moved to contact cap 12.

Various illustrative aspects of a compression-molding process forcreating a monolithic compliant member on a cap are showndiagrammatically in FIGS. 9-12. As suggested in FIG. 9, a cap (e.g., cap12) is molded or otherwise formed at a first station 301. Cap 12 is thentransported by conveyor 300 a to a second station 302 so that a plasticsmaterial formable (at a later stage) to establish a monolithic compliantmember (e.g., member 10) can be applied to cap 12. Cap 12 and theplastics material applied thereto are then transported by conveyor 300 bto a third station 303 so that the plastics material applied to cap 12can be compressed to form, for example, cap liner 11 in the interiorregion 66 of cap 12 and form grip portion 13 on an exterior surface ofcap 12. A liquid container closure 14 comprising a cap 12, cap liner 11,and grip portion 13 is now transported by conveyor 300 c to inventory304 or other satisfactory destination.

Monolithic compliant member 10 is formed using a compression-moldingmethod which includes extrusion of a plastics material 306 by anextruder 308 (or other suitable dispenser) onto the center of anunderside of a cap through a pick-up nozzle provided by extruder 308 assuggested diagrammatically in FIG. 10. A sensor 310 measures the gramweight of the plastics material 306 extruded and provides a signal viacontroller 312 to cease flow of plastics material 306 from extruder 308at a predetermined level, typically between 0.440 to 0.460 grams, for a38 mm opening cap. Cap 12 and plastics material 306 cools duringtransportation via conveyor 300 b to a compression station 303. Justprior to compression, plastics material 306 has cooled to about 215° C.and is semi-solid.

A compression punch 314 is then brought down upon the plastics material306 under high pressure generated by punch mover 316 as suggesteddiagrammatically in FIGS. 11 and 12. Compression punch 314 has a profilewhich is machined to be a mirror image of cap liner 11 having one ormore sealing surfaces as described herein. Plastics material 306illustratively adheres to cap 12 without use of adhesives or any furtheraddition of heat to cap liner 11, cap 12, or grip portion 13. It iswithin the scope of this disclosure to adhere cap liner 11 and gripportion 13 to cap 12 so as to cause cap liner 11 and grip portion 13 tohold fast or stick onto cap 12 by or as if by gluing, suction, grasping,or fusing. An illustrative apparatus for performing this method offorming a monolithic compliant member is in the KDP50-24 Plastic LinerMolding Machine sold by Oberburg Engineering AG, Ementalstrasse 137,CH-3414, Oberburg, Switzerland. Another illustrative machine would be aSacmi lining machine PMV238 available from Sacmi of Italy.

Plastics material 306 is applied to the interior surface of cap 12 assuggested in FIG. 11 and then compressed as suggested in FIG. 12 to formcap liner 11 in interior region 66 of cap 12 and form grip portion 36 onthe exterior surface of cap 12. The applying step includes the steps ofextruding plastics material 306 onto the interior surface of cap 12,determining the weight of plastics material 306 being extruded onto theinterior surface of cap 12 and ceasing the extruding step once theweight of plastics material 306 extruded onto the interior surfacereaches a predetermined weight detected during the determining step assuggested in FIGS. 10 and 11. Cap 12 includes a top wall 62 and anannular skirt 64 cooperating with top wall 62 to define interior region66 and plastics material 306 is applied to a portion of the interiorsurface located on top wall 62 as suggested in FIG. 11. In the applyingstep, for example, a molten plastics material is extruded, then cut toform a molten “pellet,” and the pellet is placed on cap 12 and arrangedto be compressed.

As suggested in FIG. 12, punch 314 is moved by punch mover 316 intointerior region 66 of cap 12 to form cap liner 11 on the interiorsurface and to move plastics material 306 through an opening 17 formedin cap 12 and plastics material 306 moved through the opening iscollected to establish grip portion 13 on the exterior surface of cap12.

1. A method of producing a liquid container closure comprising the actsof providing a cap having an interior surface defining an interiorregion, an exterior surface lying outside the interior region, and atleast one hole extending from the interior surface to the exteriorsurface and moving a plastics material through the at least one hole tocreate a monolithic compliant member having a cap liner located on theinterior surface of the cap and adapted to mate with a neck of abeverage container received in the interior region of the cap and a gripportion on the exterior surface of the cap.
 2. The method of claim 1,wherein the moving act comprises applying the plastics material to theinterior surface of the cap and then compressing the plastics materialto form the cap liner in the interior region of the cap and form thegrip portion of the exterior surface on the cap.
 3. The method of claim2, wherein the applying act comprises extruding a plastics material ontothe interior surface of the cap, determining the weight of the plasticsmaterial being extruded onto the interior surface of the cap, andceasing the extruding step once the weight of plastics material extrudedonto the interior surface reaches a predetermined weight detected duringthe determining step.
 4. The method of claim 2, wherein the cap includesa top wall and an annular skirt cooperating with the top wall to definethe interior region and the plastics material is applied to a portion ofthe interior surface located on the top wall.
 5. The method of claim 2,wherein the cap is formed at a first station and the method furthercomprises, in series, transporting the cap from the first station to asecond station, carrying out the applying step at the second station,transporting the cap and the plastics material on the interior surfaceof the cap to a third station, and carrying out the compressing step atthe third station.
 6. The method of claim 5, wherein the applying actcomprises extruding a plastics material onto the interior surface of thecap, determining the weight of the plastics material being extruded ontothe interior surface of the cap, and ceasing the extruding step once theweight of plastics material extruded onto the interior surface reaches apredetermined weight detected during the determining step.
 7. A methodof producing a liquid container closure comprising providing a caphaving an interior surface defining an interior region and an exteriorsurface lying outside the interior region and compressing a plasticsmaterial located in the interior region to create a monolithic compliantmember having a cap liner located on the interior surface of the cap andadapted to mate with a neck of a beverage container received in theinterior region of the cap and a grip portion on the exterior surface ofthe cap.
 8. The method of claim 7, wherein the compressing act includesthe steps of moving a punch into the interior region of the cap to formthe cap liner on the interior surface and to move plastics materialthrough an opening formed in the cap and collecting plastics materialmoved through the opening to establish the grip portion on the exteriorsurface of the cap.
 9. The method of claim 8, further comprising thestep of applying the plastics material to the interior surface beforethe moving and collecting steps and wherein the applying step includesthe steps of extruding a plastics material onto the interior surface ofthe cap, determining the weight of the plastics material being extrudedonto the interior surface of the cap, and ceasing the extruding steponce the weight of plastics material extruded onto the interior surfacereaches a predetermined weight detected during the determining step. 10.The method of claim 9, wherein the cap includes a top wall and anannular skirt cooperating with the top wall to define the interiorregion and the plastics material is applied to a portion of the interiorsurface located on the top wall.
 11. The method of claim 9, wherein thecap is formed at a first station and the method further comprises thesteps of, in series, transporting the cap from the first station to asecond station, carrying out the applying step at the second station,transporting the cap and the plastics material on the interior surfaceof the cap to a third station, and carrying out the moving step at thethird station.
 12. The method of claim 7, further comprising the step ofapplying the plastics material to the interior surface before thecompressing step and wherein the applying step includes the steps ofextruding a plastics material onto the interior surface of the cap,determining the weight of the plastics material being extruded onto theinterior surface of the cap, and ceasing the extruding step once theweight of plastics material extruded onto the interior surface reaches apredetermined weight detected during the determining step.